Melatonin is a naturally produced hormone that helps regulate the body's sleep/wake cycles. The amount of melatonin the body produces depends on the time of day. Endogenous melatonin levels start increasing in the evening, peak during the late night hours, and gradually start decreasing in the early morning.
Melatonin is known to have many therapeutic benefits, especially associated with sleep. It has been used to treat sleep problems such as insomnia and jet lag. It has also been used to help patients re-program their circadian clocks to account for changes in light/dark cycles due to time changes. It has also been proposed to act as an antioxidant.
Conventional oral melatonin treatments present several problems. Oral dosage forms have shown low and variable bioavailability. It can take a long time for absorption into the plasma when administered via the gastrointestinal tract. This is partly due to the fact that melatonin must first release from the dosage form, then permeate the walls of gastrointestinal tract before entering the bloodstream.
Orally-dissolving oral dosage forms also exist, but suffer from their own drawbacks. They often provide an unreliably measurable dose of melatonin to the patient. The dose a patient absorbs can vary even when the same product is administered to the same patient or different patients.